The present invention broadly relates to apparatus or machines for the manufacture of sealingly filled bags and, more specifically, pertains to a new and improved construction of an apparatus for forming, filling and sealing bag-type packages.
Generally speaking, the new and improved construction of an apparatus for forming, filling and sealing bag-type packages is of the type comprising means for infeeding a foil web from a supply roll or roller, a feed pipe or conduit for infeeding the product or material to be packed in the bag-type packages to be formed and sealed, and a formed or shaped shoulder arranged at the top or upper end of the feed pipe, the foil web being drawn over the formed or shaped shoulder in order to coil the foil web and form a foil hose or tube. Furthermore, the apparatus is provided with longitudinal sealing means for sealing the foil hose or tube in the lengthwise direction, hose conveying means for conveying the foil hose or tube along the feed pipe, and transverse sealing means for sealing the foil hose or tube at predetermined package distances and in a transverse direction relative to the lengthwise direction thereof. The transverse sealing means comprise a sealing mechanism with sealing elements operating in two stages. The transverse sealing means also are provided with stripping means which are located downstream of the sealing elements. Such stripping means are yieldable or resiliently biasable with respect to the sealing elements such that, during the first stage of operation of the sealing elements of the sealing mechanism to form the transversely disposed constrictive location in the hose, the stripping means move first up to the predetermined gap width while the sealing elements are located at a larger mutual spacing.
An apparatus of the above type is disclosed, for example, in German Patent No. 3,031,399, published Mar. 19, 1981.
This prior art apparatus comprises a feed pipe for filling or pouring in the product to be packed in packages to be fabricated of a web of flexible packing material, and a formed or shaped shoulder located at the upper end of the feed pipe. The web is drawn over the formed or shaped shoulder in order to form the web into a hose or tube. This apparatus also comprises a web forward-feed device which draws off the web from a supply or stock and conveys the same to the formed or shaped shoulder, and a hose forward-feed device arranged at the feed pipe in order to provide forward or downstream travel of the hose or tube along the feed pipe. Finally, the known apparatus comprises a transverse sealing device which is provided downstream of the feed pipe for sealing the hose or tube in package-length intervals determined by the hose forward feed. The hose forward-feed device contains a drive having a slip mechanism or device, such drive allowing for conveyance of the web in only one direction, namely in the feed or downstream direction.
It is further known, for example, from Swiss Patent No. 656,362, published June 30, 1986, to operate with so-called register or index markings, i.e. markings placed upon the web foil in adequate evenly spaced distances. Such pre-printed markings correspond with a predetermined bag or sack length and normally serve to automatically control the web forward feed of the bag forming, filling and sealing machine.
Known apparatuses or machines for fabricating bag-type packages do render possible the manufacture of bags or sacks or the like of substantially uniform length, without however taking into consideration the varying qualities and characteristics of the filling material or product.
Therefore, it can occur that the filling weight of the product or material actually remains substantially constant, this normally being the fixed parameter as required by law for the filling operation, while the volume of the product or material can substantially fluctuate or vary for a great number of reasons.
Since the bag-type package length is given by the markings on the foil web, a varying and undesired degree of filling of the bag-type package is the result of the fluctuating product volume. In order not to produce half-empty packages, also known as fraudulent or untrue weight packages, it is absolutely necessary to select the product filling quantity as a function of the smallest occurring product filling volume for the respective filling product or material. A larger product filling volume would mean that less space in the bag is available for the product, such that serious difficulties arise during the sealing operation for the bag or sack. The filling material, particularly highly voluminous and highly elastic products such as, for example, potato chips, has the tendency to expand in the region or zone of the predetermined sealing seam, so that the sealing operation, whether by sealing, welding or by any other suitable method, is rendered more difficult or even impossible.
An attempt was made to solve this problem associated with the same type of vertical bag forming, filling and sealing machines as the present development in that a so-called "stripping flat" or flattening of the package end is accomplished after filling the bag or sack with filling material but prior to carrying out the sealing operation resulting in the formation of the upper transverse seam.
A machine for accomplishing the operation of stripping or stripping-flat is shown, for example, in German Published Patent Application No. 3,046,710, published Sept. 10, 1981. This prior art machine is provided with an apparatus for stripping-flat and sealing the package end. This apparatus includes a frame, a front sealing jaw and a rear sealing jaw, the jaws being displaceable in a generally horizontal direction between an open and a closed position, whereby an actuating element is provided at the frame for moving the sealing jaws between the open and the closed positions as well as a partially open position, in which the sealing jaws approach each other but are still not completely closed in a manner suitable for sealing a package. In this partially open position, stripping elements are arranged at the sealing jaws and movable with the latter in order to grasp from opposite sides the hose or tube of packing material and nearly completely close the hose or tube, while the sealing jaws are in their intermediate position. In this intermediate position, means are connected to the frame, such means being suitable to move the frame together with the actuating element, the sealing jaws and the stripping elements, the latter being in their intermediate position. These aforesaid means are suited to effect a generally vertical and downwardly directed movement of the sealing jaws and the stripping elements relative to the hose or tube formed of packing material. In this manner, the hose or tube is internally cleared and flattened for the actual sealing operation to be accomplished by the sealing jaws which are subsequently in their completely closed position.
This known apparatus does solve the aforementioned problems of bag forming, filling and sealing apparatus of the type of the present development, but still has the disadvantage in that the entire mechanism of the transverse sealing device must be moved up and down in the vertical direction and at the high pace of bag fabrication. Due to the fact that the transverse sealing device normally possesses a relatively great mass, very high forces occur during the aforementioned up-and-down motion. Such forces must be overcome and are, in any case, detrimental with regard to the mode of operation of the machine. As a result, the maximum possible production of a bag forming, filling and sealing machine equipped with this apparatus for stripping-flat and sealing the hose forming the bags is limited by the occurring high forces.